In the 1960s and 1970s, scuba technology, underwater cameras, and documentarians revealed a long-hidden underwater world to the public. At this time oceanographic science was growing exponentially. Historians of the marine sciences have focused their studies of the period on institutional and military partnerships, and on the scientist-administrators who shaped oceanographic research institutions (such as the Scripps Institution of Oceanography, the Woods Hole Oceanographic Institution, and the British National Institute of Oceanography). Underwater habitat development during the 1960s and 1970s, however, (...) deserves greater attention than it has yet received, as it highlights a peculiar confluence of military, scientific, and popular interest, characteristic of the period, in the colonization of the seafloor. Existing accounts have focused on American habitats, notably Sealab and Tektite, since these were the largest and best funded. But this approach overemphasizes a Cold War narrative in which the sole protagonists of the habitat programs were the United States and the Soviet Union. At least 65 habitats were built between 1962 and 1991. Some were state-sponsored, with significant programs run by French, German, Japanese, and Canadian teams. This essay takes as a case study the Canadian Sublimnos habitat as well as the underwater exploration programs it helped launch in Newfoundland (Lora-I) and in the Arctic (Sub-Igloo). The Canadian case demonstrates that technological expertise and public enthusiasm for underwater exploration should not be solely understood with reference to Cold War interests of the two superpowers. Rather, the international range of habitat programs of the 1960s and 1970s reveals an expanding interest in the vertical underwater dimension that was fueled by numerous national scientific aims and territorial claims. (shrink)